1. Field of the Invention
The present invention relates to the art of electrical engineering, and more particularly to electric-arc devices. It can be applied in metallurgy for heat treatment for conductors, such as for welding and melting of metals in vacuum electric-arc furnaces and for deposition of metals by spraying.
2. Description of the Prior Art
In heat treatment of metals in vacuum electric-arc furnaces it is advisable in some cases to stabilize the position of an electric arc in the arc gap between electrodes in order to prevent the arc from getting onto the side walls of the electrodes and onto the wall of the vacuum chamber, which may result in burning through the walls of the chamber and even in an explosion. Stabilization of the arc position in the arc gap is also required in welding to provide a high quality of welding of electrodes as well as in melting of metal in skull electric-arc furnaces.
Known in the prior art is an electric-arc device (U.S. Pat. No. 2,978,525) comprising two alignment electrodes separated by an arc gap and a solenoid embracing the electrodes and mounted coaxially therewith. A uniform magnetic field produced by the solenoid in the arc gap confines the electric arc to the zone of the arc gap thus preventing it from getting onto the side walls of the electrodes and vacuum chamber. However, there is no stabilization of the arc position in the arc gap, and the arc moves between the electrodes at random.
Also known in the prior art is an electric-arc device (U.S. Pat. No. 3,636,228) comprising two aligned electrodes separated by an arc gap and a coil coaxially with the electrodes inside the negative electrode close to its working surface. In this device the electric arc under the influence of a nonuniform magnetic field produced by the coil travels over the periphery of the working surface of the negative electrode, and thus stabilization of the arc position in the arc gap is not provided as well.
Still also known in the prior art is an electric-arc device (U.S. Pat. No. 1,267,633) comprising two cylindric electrodes mounted in alignment and forming an arc gap therebetween and a means for stabilizing the arc position in the arc gap made as a cylindric coil which is arranged around the electrodes coaxially therewith in the plane passing through the middle of the arc normal to the axis of the electrodes. The coil confines the electric arc to the axis of the electrodes. The device further comprises a means for moving the electric arc over the surfaces of the electrodes, said means being at least three current conductive rods equally spaced around the electrodes and parallel to the axis thereof.
The disadvantage of the device is the substantial power consumption required to confine the electric arc to the axis of the electrodes. This results from the fact that a nonuniform magnetic field produced by the coil in the arc gap has a rather low average level of intensity and a low gradient of field intensity rise from the axis of the electrodes to their periphery. Hence, to provide an efficient stabilization of the electric arc position, a sufficiently high power consumption is required for energizing the coil. Thus, to keep a 50 A DC arc close to the axis of the electrodes 200 mm in diameter, a power supply with an output of no less than 5 kW is required for energizing the coil.
Also, in accordance with U.S. Pat. No. 1,267,633, a substantial power consumption is required to move the electric arc over the surfaces of the electrodes. This is associated with high losses of power in its delivery to current conducting rods.